Method for making semi-pyrophoric iron



UNITED STATES PATENT OFFICE METHOD FOR MAKING SEMI-PYROPHORIC IRON Alfred Schmid, Basel, Switzerland, assignor to Oswald F. Wyss, Zurich, Switzerland No Drawing. Application August 27, 1932, Serial No. 630,702. In Germany August 28, 1931 3 Claims. (Cl. 75-34) This invention relates to safety ignition mix- For many purposes ordinary metals would yield tures and to their manufacture and has for its ignition mixtures, the ignition of which would main object to provide for a safety ignition mixbe too diflicult for the purpose in question. The ture, the combustion of which takes place withinvention provides for means to bring these 6 out flame and without the production of poisonmetals into a form, in which their rapid oxidaous or bad smelling gases or of both. tion or combustion is facilitated.

The known ignition mixtures used for starting It is known, that certain metals such as iron combustion processes generally consist of the or cobalt may be obtained in the pyrophoric following constituents: form by reducing at relatively low temperatures 10 (a) Easily mposable substances yie din suitable compounds of these metals with stream- 10 oxygen by decomposition, such as chlorates, niing hydrogen. These pyrophoric metals are, trates, chromates, peroxides, and the like. however, ignited and combusted by contact with (b) Substances easily inflammable at low temoxygen or air at room temperature. This pyroperatures such as phosphorus, sulfur, carbon or phoric form of metals is not suitable for the purcompounds of the same. pose of the invention and the invention there- 5 (0) Additions of hard and chemically inert forehas for its further object, toprovide for -a substances increasing friction, such as quartz, method, which enables the manufacture of metals clay, pumice stone and the like. w in such a form, that they maybe ignited with air (it) Binding agents such as "glue, starch, gum at temperatures above atmospheric temperature, arabic and the like. preferably above 50 C. but below 300 C. I-have 2 (e) Substances preventing an explosive comnamed this form of metals semi-pyrophoric, bustion such as zinc oxide, iron oxide and the which is, an intermediate form between pyrolike, phoric and normal form. This method for mak- Due to the presence of the substances mening' semi-'pyrophoric metals consists in a reductioned under I) all known ignition mixtures are tion of metalcompounds suitable for the manu- 25 combusted with flames and evolution of poisonous facture of pyrophoric' metals under such modior evil smelling gases or of both. Their use is fied reducing conditions that neither the pyrotherefore impossible in all those cases where open phoric. nor the normal form is obtained or in flames of the evolved gases are dangerous or treatment of pyrophoric metals which makes noxious. them more diflicultly ignitable. The reduction 3 The present invention provides for a safety igof the metal compounds may be carried out by nition mixture which may easily be ignited on thermal decomposition in presence of inert gases the usual friction surfaces for safety matches or by treatment with hydrogen at raised temperand are combusted without flame and without atures. I

evolution of noxious or evil smelling gases. Self- A metal is semi-pyrophoric when, on the 35 ignition of the new ignition mixtures is imposone hand, it is not self-ignitable by mere consible. The new ignition mixtures are especially tact with air and, on the other hand, is not so suitable as igniting heads for cigars, cigarettes diiiicultly ignitable as in the normal state but can and matches, which are safely and efllciently be brought into a state of ignition by friction-on 4o lighted by mere friction on one of theusual frica friction surface. Or, in other words, a metal is 40 tion surfaces for matches, which surfaces are semi-pyrophoric when its ignition temperapreferably arranged on or in the packages for t the cigars, cigarettes matches (1) Is not so low that it ignites by contact with According to the invention the phosphorus, sulfur or the like present in the known ignition Is not so high t t it does not ignite by 45 mixtures is replaced by metals with a sufficiently gig i fi gi ggf ggs fi gg fi igi ifiga (3) But is of such a nature that mere friction on combustion do not furnish volatile combustion on lfnctlon surface Sumclent lgmtmg the products but solid oxides in form of a powder. meta 50 The main feature of the new ignition mixtures is Temperature and @I these trfeatments the absence of phosphorus, sulfur, carbon or their must be kept Within 11ml, ut51de 0f Whlch P compounds, the inflammability f th mixture phoric or normal metals are obtained. Starting being solely due to the combination of oxygen materials for the method according to the invenyielding substances with easily ignitable metals. tion are inorganic or organic metal compounds 55 friction on a friction surface;

such as oxides, nitrates, carbonates, sulfates, oxalates, tartrates or the like.

Pyrophoric metals may be converted into semipyrophoric metals by a shorter or longer heat treatment in presence of inert gases, such as nitrogen, hydrogen and the like or by mixing or alloying them with substance, not self-ignitable by contact with air, such as oxides.

In both cases for the manufacture of semipyrophoric metals the duration of the treatment is a function of the temperature. Moreover temperature and duration of the treatment are different for diiferent metals, gases and pressures employed. It is therefore not possible to give general data for temperature and duration of the-treatment, but the following examples may lead the expert in finding the conditions for making semi-pyrophoric' metals other than iron or semi-pyrophoric iron from other starting materials or by a modified method.

Example I 10 g. of ferrous oxalate are heated to about 400 C. in streaming hydrogen, which has been dried by passing it through concentrated sulfuric acid before entering the reaction zone and which passes this zone at a moderate rate corresponding to about two gas .bubbles leaving the sulfuric acid per second. When the amount of gases leaving the reaction zone decreases, which is the case after about one hour, the reaction is finished. The heating is stopped and a rapid cooling is effected by passing hydrogen through the reaction zone. When room temperature has been reached a black powder is obtained not ignitable by contact with air, at room temperature, but ignitable, when contacting it with air at about 180 0.

Example II 28 parts of the semi-pyrophoric iron produced in the manner described are mixed with 25 parts of potassium chlorate, 1 part of pyrolusite and 18 parts of powdered burnt clay. The mixture is powdered and mixed while stirring with80 parts of a 4% solution of collodion in volatile organic solvents, some ether and alcohol being added to the pappy mixture if necessary. The mixture is placed on the top of a cigar or cigarette in any convenient manner, thus obtaining a firmly adhering ignition head on the article after evaporation of the volatile solvent at the air.

The igniting mixture described above may contain other substances, such as fillers and the like, or may be combined with other pyrotechnic mixtures. It may be arranged on any inflammable carrier and thus serve to light any combustible substance.

The solution of collodion employed as binding agent in the above example may be replaced by solutions of other binders, such as acetyl cellulose and the like, in volatile organic solvents,

such as alcohol, ether, acetone, amyl acetate and the like. Also aqueous solutions of glue, starch, gum arabic and the like may be employed, although binders containing volatile organic solvents are preferred, as the solidification of the ignition mixtures on their carriers is accelerated, when the binder contains volatile liquids as solvent. The amount of binder used is kept as low as possible and preferably such binders are employed, which are easily and completely combusted without the evolution of noxious or bad smelling gases or of both.

I claim:

1. A method for making semi-pyrophoric iron which consists in reducing iron compounds with hydrogen at reaction conditions with respect to temperature and duration of reaction, above which pyrophoric and below which normal iron are obtained, iron oxide being used as starting material.

2. A method for making semi-pyrophoric iron which consists in reducing iron compounds with hydrogen at reaction conditions with respect to temperature and duration of reaction, above which pyrophoric and below which normal iron are obtained, ferrous oxalate being used as starting material.

3. A method for making semi-pyrophoric iron which consists in a reduction by means of hydrogen of iron compounds at increased temperature, keeping the conditions of reaction with respect to temperature and duration within limits, beyond which pyrophoric and normal iron respectively are obtained by the same treatment.

ALFRED SCHLHD. 

